Vinyl resin textile article



March 7, 1950 T. A FEILD, JR

VINYL RESIN TEXTILE ARTICLE Filed June '7, 1945 R. J R w.. Y La o T E T F. N WW w. F. v A N w. l A 7N w H c Pnm F, n 0 R ...H.. T S T m n w o msmo .33%2 2.0L n0 7., H. C c n R T /lf s C .wl m w n G. 0 wf .33%2 momo.

Patented Mar. 7, 1950 vmrL mism 'rax'rmn ARTICLE Theophilus A. Feild, Jr., Charleston, W. Va., al-

signor, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation oi New York Application :une 1, 1945, serial No. 59am 4 claims. (ci. s-1so.1

This invention relates to a process for improving filaments, threads, yarns and various textile articles made from or containing oriented lilaments and nbers formed of vinyl resins produced by the conjoint polymerization of a vinyl halide with acrylonitrile, and to the novel heat treated textile articles thereby produced. More especially it concerns a heat treatment of such textile articles whereby certain important latent properties of the resin are developed, with resultant significant changes in the yarn characteristics. The invention has especial utility for the treatment of filaments and yarns made from such resins by the usual dry-spinning and wet-spinning of acetone dispersions of the resins.

While the shrinkage of the yarn, and of fabrics made therefrom, at elevated temperatures around 100 C., is minimized, the elastic recovery of the original yarn is largely retained; the tensile strength at ordinary temperatures is largely preserved; and the strength of the yarn at elevated temperatures of the order of those used in the heat treatment or less, is improved. Concurrently the solubility of the yarn in acetone is greatly reduced or eliminated, the yield point of the original yarn is largely retained and the strain' release point of the yarn is elevated. In the case of knitted and woven fabrics made from such yarns, the process provides articles of exceptionally clear stitch formation with excellent dimensional stability in water or steam at 100 C.

Filaments, bers, yarns and other textile arti'- cles made from vinyl resins produced by the conjoint polymerization of a vinyl halide and acrylonitrile are now lmown. Resins capable of being formed into filaments, yarns and fabrics that are especially benefitted by the process, are the acetone-soluble copolymers of a vinyl halide and acrylonitrile, having between about 45% and about 80% of the halide in the polymer,I and having specific viscosities at 20 C. within the range between around 0.2 and around 0.6. These resins may be produced by the emulsion polymerization of vinyl chloride and acrylonitrile in the presence of a catalyst such as benzoyl peroxide. Such a process is described in the pending application, Serial No. 488,508, of L. C. Shriver and G. H. Fremon, filed May 26, 1943, now Patent No. 2,420,330.

The filaments may be spun from a dispersion of such resin in acetone or other suitable spinning solvent, using either the dry spinning or the wet spinning procedure. A thread or yarn of the desired denier is then formed by twisting the laments by any well-known procedure. after which the yarn is stretched at least 200% while exposed to temperatures between around 100 C. and around 250 C., and preferably between 120 C. and 140 C., for imparting thereto increased tensile strength and the property of true elasticity. This may be accomplished by passing the ing from 100 C. upwardly to somewhat below the stretching temperature, to reduce the shrinkage thereof when exposed to temperatures around 100 C., and to increase the elongation of the yarn and improve its flexibility. The resultant yarn, however, possessed a yield point considerably lower than the yield point of the unstabihzed yarn, and had less desirable elasticity and hysteresis characteristics than the latter.

Among the more important objects of this invention are: the production of stretched laments, fibers, threads, yarns and other textile articles from resinous copolymers of a vinyl halide and acrylonitrile, which articles have good tensile strengths, relatively high yield points, good fatigue-resistances, elasticity and thermal stability, and greatly increased tensile strengths at elevated temperatures; the production of such textile articles which, while remaining largely thermoplastic, have their solubilities in acetone and other spinning solvents reduced to a low value or substantially eliminated, thereby increasing the resistance of the articles to attack by such solvents,

even at elevated temperatures; to provide for reducing the residual shrinkage in a stretcher. filament, yarn or fabric of such a resin, while preventing undue lowering of and even increasing the yield point of the yarn or fabric, and providing an article having excellent dimensional stability 'at temperatures of around 100 C. to 120 C. These and other objects will be evident fromA the following description of the invention.l

Yarns stabilized by the heat treatment of the` invention commonly have tenacities of 2 grams or more per denier and wet elongations of not less than 10%, in conjunction with a shrinkage of not more than 7% in water at 100 C., and of not ative vinyl chloride-acrylonitrile resin yarn of v the type described herein upon heating the stetched yarn while under tension to C. for various periods in accordance with the invention;

, Figs. 2 and 3, respectively, show representative curves A, B and C secured by recording the progressive increase in length of such yarns under a constantly increasing tensile stress; and

Figs. 4 to 6, respectively, show curves indicating the progressive loss of true elasticity and increase in elongation upon subjecting representative yarns iive time to a tensile force onehalf the breaking strength of the yarn.

In accordance with one modification of the invention, a stetched oriented yarn, lament or the like of a vinyl chloride-acrylonitrile copolymer resin is treated with a material which, while inert to the resin, is capable, upon drying, of temporarily bonding a stretched yarn, or a textile article made therefrom, to a rigid surface, or of sealing or bonding the threads of a yarn cake into a rigid mass, to render the yarns incapable of shrinking upon the application of dry heat. Usually the binding material is water-soluble, or is capable of forming suspensions or emulsions with Water. The bonding material may be, for example, a water-soluble size-e. g., a watersoluble cellulose ether, or a partially hydrolyzed polyvinyl acetate-or an aqueous suspension of an inorganic material, such as bentonite or a saturated solution of sodium bicarbonate. It can be supplied to the stretched yarn as it is wound under tension into a yarn cake. This cake then is dried, commonly at temperatures around 60 C. or below, to remove water, whereupon the cake becomes hard and the yarn turns are held rigidly in place.

I'he dried yarn cake then is heated with dry heat to an elevated temperature at least as high as, and preferably higher than, the temperature used in stretching the yarn. Dry heat is required because water tends to have a plasticizing effect on the yarn at the elevated temperature used. Effective heat treatments within the scope of this invention are conducted at temperatures ranging from around 120 C. to 175 C. for periods of time ranging from 1 minute to as much as 48 hours, the higher temperatures being used with the lower periods of exposure to such heat. It is preferred to conduct the heat treatment at temperatures ranging from around 150 C. for periods of from 1 to 4 hours Ato 175 C. for periods of from 2 minutes to 1 hour.

Following this heat treatment the yarn cake is washed or soured with water or the equivalent to remove the bonding agent. 'I'he yarn may then be packaged in conventional manner. Spooling; skeining and coning of the yarn may be readily performed.

The heat treatment of the invention may be eectively applied to filaments and yarns of these resins without the aid of the aforesaid bonding materials, as evidenced by Example II.

An outstanding and unobvious feature of the invention is the eifect of the heat treatment in reducing the acetone solubility of the stretched oriented yarns, etc., of acetone-soluble vinyl halide-acrylonitrile copolymer resins while causing the resin to develop a crystalline structure, and while preserving other desired physical properties of the yarns adapting them for service as textile materials. Indeed, at temperatures around 150 C.` the reduction in acetone solubility occurs very rapidly, and often is over 80% complete in an hour. (See Fig. 1.) At temperatures of 120 C. a period of nearly 48 hours is required for the same conversion, while at 175 C. less than 5 minutes are required. Thus, by subjecting the stretched yarn to heat Within the temperature range from 120 C. to

around 175 C. while under tension, for periods of 2 minutes or more, depending on the temperature used, stretched or oriented yarns of vinyl halide-acrylonitrile resin lose a large part, and.

even the major part or all of their solubility in volatile solvents such as acetone, and develop a crystalline structure. This reduction in acetone solubility produced by the present heat modification treatment is not of. general application to thermoplastic resin yarns. Thus, yarns made from copolymers of vinyl chloride and vinyl acetate, and those made from after-chlorinated copolymers of vinyl chloride and vinyl acetate, are not benefitted by the process.

A very important and unobvious feature of the invention is the great improvement in the tenacity and elongation of the yarn at elevated temperatures as a result of the heat treatment. Many uses of textile fabrics require that the latter shall have good tensile strengths at elevated temperatures-especially those around C. and above. Example I, and the data appearing in Table 1, show that a heat treatment of a stretched yarn at 150 C. for 1 hour and 3 hours, respectively, increased the tenacity of the yarn at 120 C. by 43% and 87%.

The invention is applicable for the treatment of woven, knitted and other textile fabrics made from yarns of the vinyl halide-acrylonitrile copolymer resins. Hosiery and other knitted fabrics of excellent stitch and fabric clarity which possess good dimensional stability at temperatures even above the boiling point of water have thus been produced. Fabrics made from unstabilized stretched yarn, as well as fabrics made from stretched yarn that has been given a preliminary stabilization treatment in steam or hot water at elevated temperatures up to around C., may be used.

The fabrics made from stretched yarns of vinyl chloride-acrylonitrile resins are especially useful in industrial filter fabrics because of their resistance to attack by many chemicals. Often liquids must be ltered hot. It then is important that the filter fabric has dimensional stability at the temperature of use of such fabrics.

Heretofore, in order to reduce the shrinkage at elevated temperatures of yarns and textile articles made from these resins, the stretched yarns have been heated in the untensioned state to ternperatures around 100 C. to 110 C. in steam or moist heat. While such treatment eiectively reduces the shrinkage of the yarn at temperatures around 100 C., the treated yarn often has an objectionable tendency to yield under the action of the low stresses applied during textile fabricating operations. Similar deformation of the resultant fabric sometimes occurs during normal use. The elasticity and fatigue-resistance of the yarn are much reduced by this prior treatment.

By the high temperature dry heat treatment of this invention, it is now possible to minimize or eliminate the shrinkage of the oriented yarn or fabric upon exposure thereof to temperatures around 100 C. or even higher. Concurrently Y the ductility of the yarn-'1. e., the extent of permanent elongation of the yarn, or of textile articles made therefrom, when the yarn is subjected to low stresses at ordinary temperatures of use-is greatly reduced. (Compare Figs. 5 and 6.)

This is exemplified in Figs. 2 to 6 of the drawing wherein are shown representative curves secured by recording the progressive increase in length of a yarn under a constantly increasing l tensile stress, using a Scott Inclined Plane tensile tester being marketed by Henry L Scott Co., Providence, R. I. Curve A of Fig. 2 shows the progressive elongation of a yarn made of a vinyl chloride-acrylonitrile copolymer resin, which yarn had been stretched 1289% at 127 C. and,v after stretching, had 4been stabilized in the untensioned state by heating the yarn for 1 hour at 100 C. in steam. Curve B of Fig. 2 is a representative curve showing the progressive elongation of a yarn similar to that of Curve A but which, after stretching, had been stabilized in the untensioned state by heating the yarn for 3 hours at 150 C. with dry heat. Curve C (Fig. 3) is a representative curve showing the progressive elongation of a yarn similar to that of curve A but which, after stretching had been stabilized in dry heat at 150 C.' for 3 hours while under tension preventing. shrinkage. and C had deniers of 36, 44.5 and 30, respectively, and tenacities, respectively, of 4.85, 3.31 and 4.31 grams per denier.

Curve D (Fig. 4) illustrates the progressive loss in true elasticity and permanent increase in elongation which occurs upon subjecting the yarn of curve A ve times to a tensile force onehalf the breaking strength of the yarn. Curve E (Fig. 5) illustrates the increased elongation of the yarn of curve B and reduction in its true elasticity which occurs upon subjecting the yarn five times to a tensile force one-half the breaking strength of the yarn. Curve F (Fig. 6) illustrates the outstanding improvement in the true elasticity ofthe stabilized yarn resulting from this invention, and evidenced upon subjecting the yarn of curve C five times to a tensile force onehalf the breaking -strength of the yarn.

It will be seen from the curves A, B, D and E that, in the case of yarns heat treated while untensioned, the elongation increases with the temperature of the heat treatment and tends to become excessive, even at heating temperatures around 100 C. The curves D, E and F indicate that, while the yarn of curve D recovered 19% of its original length upon release ofstretching tension, and the yarn of curve E recovered 20%, the yarn of curve F, which was treated in accordance with the invention, recovered about 38%. The yarn of curve F had an elastic recovery, after the iinal tension release, about twice that of the yarn of curve D stabilized at 100 C. while untensioned; and the former had a fatigue-resistance over twice that of the latter, and an elongation under load around 30% of the latter.

In addition to the improved elasticity characteristics imparted to the yarn by the heat treatment of this invention, the improvement of another property of equal importance is well illustrated by the curves in the drawing. Yarns having low yield points are very susceptible to distortion and injury even in normal fabricating operations due to the low tensions applied in the usual knitting and weaving operations. Comparing curves A, B and C it will be seen that a' much smaller load per denier is required to elongate the yarn of curves A and B than for curve C. In fact a load of about 1 gram per denier produces a 3% extension in the yarn of curve B while 1.5 grams per denier or a 50% greater load is required for the same extension of the yarn of curve C. Also it will be noted that when about 50% of the breaking load is applied to the yarn of curve C the iiber elongates only about 7% while in curves A and B the extension is more than double this value.

The yarns of curves A, B,

6 The following examples serve to illustrate the invention:

EXAMPLE I solubility of the yarn was determined at interj vals during this period by agitating 1 gram of the yarn for 2.5 hours in 35 cc. of anhydrous acetone maintained at 40 C. The total solids content of the liquid then was determined. The percentage solubility was based upon the original weight of the sample. The tensile properties of the yarn were determined at C. in dry heat at the same intervals. The heat treated yarn had the properties indicated in Table 1:

Table 1 Dry Dry Acetone Tenacity Elonga- Soluble, grams per tion, Per cent denier Per cent TESTED AT 120 C.

Original stretched yarn-unstabilized 0. 79 18. 8 100 stretched yarn steam stabilized at 100 C. untensioned 1 0. 63 20. 2 Heated under tension 1 hour at 1. 13 18. 8 18. 2 Heated under tension 3 hours at 1. 48 19. 3 3. 1 Heated under tension 6 hours at l. 57 19. 0 4. 9 Heated under tension 9 hours at 1. 58 19. 2 f 3. 2 Heated under tension 12 hours at 1. 68 20. 0 0. 8 Heated under tension 24 hours at C l. 85 16. 5 2. 3 Heated under tension 1.5 hours at TESTED AT ROOM TEMPERATUREl Original stretched yam-unstabilized 5.02 10.7

1 For comparison.

EXAMPLE II A quantity of a 35 denier 40 filament acetonesoluble vinyl chloride-acrylonitrile copolymer resin yarn, stretched 1289% at y127 C. was wound onto small glass bobbins and jheated at 120 C. with dry heat for 48 hours. The resin had a vinyl chloride content of 59.1% and a specific viscosity at 20 C. of 0.277. Table 2 illustrates the resultant great reduction in the shrinkage capacity of the yarn at temperatures around 100-110 C., and the loss of the major portion of -the acetone solubility of the yarn.

Other supplies of the same yarn were heated on small glass bobbins under tension for 1 minute and for 2 minutes, respectively, in a liquid mixture of molten polyoxyethylene glycols maintained at C. Table 2 shows that a marked reduction in the acetone solubility of the yarn and a large reduction in the shrinkage of the yarn in water at 100 C. were seccured by this brief heat treatment.

' maintained at 160 C., under conditions such that the yarn, under tension, was exposed to this temperature for 29.5 minutes. The heat treated yarn 8 EXAMPIEIV Stabilization of fabric prepared from unstabilzed yarn A 35 denier yarn made from a vinyl resin produced by the conjoint polymerization of vinyl chloride and acrylonitrile and containing 60.8% of the chloride in the polymer and having a specic viscosity at C. of 0.402 was stretched had the properties indicated in Table 2: 10 l289% at 132 C. This stretched but unstabl- Table 2 Yarn shrinkage Heat- Wet me gag@ .o Mm Para m no lr denier Minutes, Soluble o pe Per Cent Water at Steam Steam 100 c. at 110 110120 Unheated 5. 44 10. l 17. 6 100 120 6.23 14s 6.0 9.0 18.1 14.1 130 3.81 14.8 5.66 8.1 22.0 13.0 150 4.05 16.0 .5.0 6. 6 13.3 41.6 160 4.40 14.5 6.5 0.4` 14.0 69.4 115 4.31 18.0 6.84 21.1 29.4 61.8 115 3.86 2&0 0.2 9.2 18.3 65.2

EXAMPLEIII lized yarn was tube knit, and the fabric was scoured and then immersed for 15 minutes in a A quantity of a vinyl chloride-acrylonitrile resin stretched yarn of 65 denier was wound onto a spinning bobbin from a 6% aqueous suspension of bentonite. The resin contained 63.1% of the chloride in the polymer, and had a specific viscosity at 20 C. of 0.379. The yarn had been stretched 1005% at 136 C., and thereafter had been heated for 1 hour in steam at 100 C. in an untensioned condition to stabilize the yarn. The resultant yarn cake containing the bentonite was dried at around 100 C. to form a rigid mass. It then was subjected to dry heat at 150 C. for 3 hours. The yarn cake then was washed with water to remove the bentonite, and was ready for use or further treatment.

The heat treated yarn thus produced had a much improved yield point, a greater fatigueresistance and a much higher strain release temperature than the same yarn before such treatment. The yarn was largely insoluble in acetone, although the yarn prior to the heat treatment was acetone soluble. A comparison of the properties of the yarn before and after the heat treatment appears in Table 3:

Table 3 Wet elon- Wet Tenacxty, Sample Denier grams/denier Iartxcn Original-Stabilized Yam 66 3.15 29.0 Heated-3 hours at 150 C 66 3. l5 25. 7

Shrinknge Time, shrinkage Temperature Ori Stabilized gmwl Stabilized Ym Heated Yam or 3 Hrs. at 150 C.

Per cent Per cent 30 Min. in Water at 100 C 0.30 1. 6 l5 Min. in Steam at 120 C 3.2 15 Min. in Steam 31130 C 5. l 15 Min. in Steam at 135 C 8.8 15 Min. in Steam at 140 C 22. 3

5% aqueous solution of a water-soluble hydroxyethyl cellulose. The sized fabric was placed on an aluminum form to prevent shrinkage and was air dried to thoroughly bond the fabric to the form. The form and dry fabric were heated at 150 C. for 3 hours with dry heat. Thereafter EXAMPLE V A quantity of a 30 denier stretched but unstabilized yarn made from a vinyl chloride-acrylonitrile copolymer resin was thrown for hosiery, and was sized with a partially hydrolyzed polyvinyl acetate containing 3.5% boric acid for controlling the high twist of the lyarn. The said y resin contained 60.8% of the chloride in the polymer, and had a specic viscosity at 20 C. of 0.402. The yarn had been stretched 1289% at 132 C.

After knitting, looping and seaming, the resultant hosiery made from the unstabilized yarn were lightly scoured to remove oils and size. The Wet, clean hosiery were next immersed in an 8% aqueous suspension of bentonite for at least 10 minutes and then were placed on suitable hosiery forms and thoroughly air dried and bonded to the forms while under tension. The forms and hose then were heated with dry heat for 3 hours at C. The heat treated hosiery were dimensionally stable, even after being dyed at a boil with acetate type dyestuis. The hosiery were finished in the standard manner. The fmished hosiery were dimensionally stable in boily to' the heet treatment of the invention. The fabrics thus produced by the treatment of this .invention possessed good dimensional stability ln boiling water, and improved elasticity and elastic recovery.

Table 4 illustrates the important advantages secured by the heat treatment of the invention, applied while the yarns were maintained under tension, as contrasted with a treatment of yarns at similar temperatures under conditions permitting free shrinkage to occur.

Table 4 In this table A designates a vinyl chloride-acrylonitrile resin yarn which has been stretched 1289% at 130 C., here identified as yarn Y, whichfyarn Y has been heat treated 1 hour at 100 C. in steam while permitting free shrinkage;

' B designates yarn Y which has been heat treated 3 hours at 150 C. with dry heat while under tension; C designates yarn Y which has been heat treated 3 hours at 150 C. with dry heat while permitting free shrinkage; D designates yarn Y whichhas been heat treated 9 hours at 150 C. with dry heat while under tension; E designates yarn Y which has been heat treated 9 hours at 150 C. with dry heat while permitting free shrinkage; F designates yarn Y which has been heat treated 1% hours at 160 -C. with dry heat while under tension; and G designates yarn.Y which has been heat treated 11/2 hours at 160 C. with dry heat while permitting free shrinkage.

It will be noted that while heat treatments for 1.5 hours and more at temperatures around gave products which had low shrinkage values when subsequently exposed to temperatures of 100 C. and above, the dry elongation of the yarn resins which have been heat treated in accordance with this invention surprisingly have their safe ironing temperatures much increased thereby. 'I'his is illustrated in the following example:

EXAMPLE VI A tubeknit fabric was made from stretched yarn of a vinyl chloride-acrylonitrile copolymer' resin containing 58% of the chloride in the polymer and having a specific viscosity at 20 C. of .350. The stretched yarn had been heated with free shrinkagein steam at 100 C. for 1 hour. The

' 150 C.160 C. applied to the untensioned yarn fabric was immersed in a 6% aqueous suspension of bentonite, slipped on an aluminum form and allowed to dry. When thoroughly bonded to the form the fabric was heated by dry heat for 3 hours at 150 C. The fabric was then washed from the form with water.Y

The heat-modified fabric was then tested to determine its safe ironing temperature, using a. Sunbeam electric iron with temperature control and a spot pyrometer. The following results were secured:

. Maximum Material Sale Temperatnre .F. The fabric prior to heat treatment. m The fabric atta heat treatment as above 270 The invention is susceptible of modification within the scope of the appended claims.

I claim:

1. A heat treatedoriented synthetic textile yarn of filaments lformed from a copolymer of a vinyl halide with acrylonitrile, which copolymer contains between about 45% and about 80% of the halide and has a specific viscosity at 20 C. of be.

tween 0 .2 and 0.6, saidv yarn having an acetonec solubility of not more than 75% of that of the copolymer from which the yarn was made, and having a wet tenacity of at least 2 grams per denier, a tenacity of 120 C. of over I gram per denier, a wet elongation of at least 10%, and shrinkages of not more than 7% in Water at 100 C. and of not more than 30% in steam at 120 C.

2. A textile fabric made of heattreated oriented cosity at 20 C. of between 0.2 and 0.6, said yarn having an acetone-solubility of not more than 75% of that of the copolymer from which the yarn was made, and having a wet tenacity of at least 2 grams per denier, a tenacity at 120 C. of over 1 gram per denier, a wet elongation of at least 10%, and shrinkages of not more than 7% in water at C. and of not more than 30% in steam at C.l

3. A heat treated oriented synthetic textile yarn of filaments formed from a copolymer oi' vinyl chloride with acrylonitrile, which copolymer contains between about 45% and about 80% of the chloride and has a specific viscosity at 20 C. of between 0.2 and 0.6,said yarn having anacetone-solubility of not more than 75% of that of the copolymer from which the yarn was made, and having a wet tenacity of at least 2 grams per denier, a tenacity of 120 C. of over 1 gram per denier, a .wet elongation of at least 10%, and shrinkages of not more than 7% in .water at'100 C. and of not more than 30% in steam at 120 C.

4. A textile fabric made of heat treated oriented synthetic textile yarn of filaments formed from a copolymer of vinyl chloride with acrylonitrile, which copolymer contains between about 45 and about 80% of the eloride and has a specific viscosity at 20 C. of between 0.2 and 0.6, said yarn having an acetone-solubility of not more than '75% of that of the copolymer from which the yarn was made, and having a wet tenacity of 'at least 2 grams per denier, atenacity at 120 C. of over l gram perdenier, a wet elongation of at l least 10%, and shrinkages of not more than 7% Number 1n water at 100 C. and of not more than 30% 1n 2,321,746 steam at 120 C. 2,332,974 TI-IEOPHILUS A. F'EILD, JR. 2,339,323 5 2,346,208 n REFERENCES CITED 2,366,495 The following references are of record in the 214209565 me of this patent: -2421334 UNITED STA'I'ES PATENTS lo Number Name Date Number 2,293,825 Hosnela Aug. 25, 1942 513.327 2,309,370 wnuams Jan. 2e, 1943 513.354 2,313,173 Schneider et al Mar. 9, 1943 Name Date Heymann June 15, V1943 Lytton Oct. 26, 1943 Feild Jan. 18, 1944 Conaway Apr. 11, 1944 D'Alelio Jan. 2, 1945 Rugeley et al May 13, 1947 Kline et a1 May 27, 1947 FOREIGN PATENTS Country n Date Great Britain Oct. 10, 1939 Great Britain Oct. 10, 1939 

2. A TEXTILE FABRIC MADE OF HEAT TREATED ORIENTED SYNTHETIC TEXTILE YARN OF FILAMENTS FORMED FROM A COPOLYMER OF A VINYL HALIDE WITH ACRYLONITRILE, WHICH COPOLYMER CONTAINS BETWEEN ABOUT 45% AND ABOUT 80% OF THE HALIDE AND HAS A SPECIFIC VISCOSITY AT 20*C. OF BETWEEN 0.2 AND 0.6, SAID YARN HAVING AN ACETONE-SOLUBILITY OF NOT MORE THAN 75% OF THAT OF THE COPOLYMER FROM WHICH THE YARN WAS MADE, AND HAVING A WET TENACITY OF AT LEAST 2 GRAMS PER DENIER, A TENACITY AT 120*C. OF OVER 1 GRAM PER DENIER, A WET ELONGATION OF AT LEAST 10%, AND SHRINKAGES OF NOT MORE THAN 7% IN WATER AT 100*C. AND OF NOT MORE THAN 30% IN STEAM ATR 120*C. 